PROJECT SUMMARY The overall goal of this application is to facilitate the necessary training the applicant requires in order to successfully launch an academic research career. In the long-term, the applicant seeks to develop an independent program of research focused on designing and evaluating intervention innovations that lead to improved mental health outcomes for difficult-to-treat and difficult-to-reach youth. To this end, the current proposal includes a set of training goals and corresponding experiences that will strategically advance the applicant?s knowledge of existing barriers to and innovations in treatment delivery, as well as the development of skills related to the design, conduct, and analysis of modern clinical trial methodologies that can be used to enhance and extend the reach and scope of supported care for youth psychopathology. Substantial barriers to and disparities in access and utilization of mental health care have traditionally hindered the reach and impact of valuable youth mental health interventions. Problems with the accessibility, availability, and acceptability of evidence-based treatments (EBTs) are especially pronounced for youth with low base rate problems or who require complex treatments and high clinical expertise. Recent work evaluating intensive treatments?i.e., a full course of treatment offered via massed sessions over a condensed period of time?and remote technologies?e.g., delivering EBTs to families in impaired settings in real-time via videoconferencing? have both demonstrated success in overcoming limitations to quality and generalizable care for such difficult- to-treat and/or difficult-to-reach youth. However, research evaluating which subpopulations of youth, under which particular conditions, respond best to which treatment format sequences has been limited. The project at the center of this training fellowship will examine key factors associated with acute and longer- term outcomes of a post-acute telehealth continuation/transition planning strategy that leverages intensive group behavioral treatment (IGBT) for childhood selective mutism (SM) followed by online, videoconferencing- based ?booster? sessions. All participating families (N=69) will complete (or have already completed) a 5-day IGBT for SM and will be included to pursue Aim 1, and a subset (n=20) will be randomly assigned to either receive 6 biweekly videoconferencing-delivered ?booster?/generalization sessions across 12 weeks or no additional treatment to pursue Aims 2 and 3. Aim 1 will examine whether child severity and child responsiveness to reinforcement strategies predict acute IGBT treatment outcomes (i.e., improvement, remission, functioning). Aim 2 will evaluate differences in child improvement, remission, and functioning between IGBT-treated families who receive post-IGBT online ?boosters? and IGBT-treated families who do not receive post-IGBT online ?boosters? 16 weeks after the initial IGBT. Finally, Aim 3 will examine whether acute IGBT outcomes, interim child symptom relapse, interim parental skill acquisition, or technological literacy predict or moderate outcomes 16 weeks after the initial IGBT.